Dunno why OP.
Maybe something to do with the PEGI rating of the game? dunno what the rules are around selling 'alcohol?' to minor's in a computer game
Likely though to be animation & coding.
You get a drink at the bar, you need to ask for it......choice appears
pay for it.......credit reduction from account noted & appears on screen.
Once you've got it, you then need to be able to drink it.......knock it back or sip?.......requires animation rather than just going into our 'inventory' like everything else does

.
Then do you have to have some sort of drunken indicator monitoring how much you've taken in & maybe then start getting staggering movement?
Suggestions then go on & on......
One good thing is that the Devs introduced the emotes recently for stuff like saluting, waving, etc. So they could have one for a drink movement.
Bad thing is that there's very little 'hand' interaction in Odyssey, you never 'pick' anything up in-game, it alway goes straight to your inventory or appears in our hand in front of us like the scanner & tools do.
It's up to the Dev teams to decide whether it's worth their time against what benefits they feel it provides to game play........at launch they thought it didn't, along with sitting down on seats.
Maybe they'll surprise us & bring these into the game in the near future.........there were a lot of seats in that Carrier trailer
As for illegal Missions.....RUBBISH! there's loads of LEGAL Missions to be had, where are you looking OP?